A cylinder head of an internal combustion engine contains the cylinder or cylinders. The cylinder head has a respective exhaust port from each cylinder. Each such port communicates with a common exhaust manifold for the engine. The exhaust manifold includes inlet pipe sockets that are connected to the exhaust ports from each cylinder in the cylinder head. The exhaust manifold is considerably heated by the exhaust gases passing through it. The cylinder head, on the other hand, is kept relatively cooler by appropriate cooling means provided therein.
Typically, an exhaust manifold is fastened by appropriate fastening means to the cylinder head from whose cylinder that exhaust manifold is fed. However, fastening of the exhaust manifold to the cylinder head of a multi-cylinder internal combustion engine is difficult. This arises in part because of the different rates of thermal expansion of the exhaust manifold and of the cylinder head. It does not matter whether there is a single exhaust manifold for several cylinders that are in a single cylinder head or whether there is a single exhaust manifold for an engine having a respective individual cylinder head for each cylinder. The different rates of thermal expansion result from the large difference in temperature between the generally uncooled exhaust manifold and the generally cooled common cylinder head or the generally cooled crankcase in the situation of an individual cylinder head containing only an individual cylinder. The different rates of thermal expansion may cause warping of the exhaust manifold and/or of the pipe sockets of the exhaust manifold which communicate with the exhaust ports from the cylinder head. It may even lead to cracks or breaks developing in the exhaust manifold or its pipe sockets. It may also lead to the destruction or leaking of the gaskets that are generally installed between the exhaust manifold and the cylinder head at the points of connection therebetween. Further, it also may break the fastening elements by which the exhaust manifold and the cylinder head are connected.
One known solution to the problem of different rates of thermal expansion comprises connecting an elongated resilient transition pipe between the exhaust manifold and the point of connection of that manifold with the cylinder head for elastically taking up the relative distortions resulting from the different rates of thermal expansion. This solution, however, is expensive, increases the weight of the entire connection and of the exhaust manifold assembly and requires a large amount of space in the engine compartment of the vehicle.